A rapid and sensitive imaging method for detection of active internal bleeding can improve patient outcome in trauma by enabling early and effective management decisions. Such an imaging method can also provide image- guided treatment and monitoring capability for future intraoperative and noninvasive hemostasis techniques, such as high intensity focused ultrasound. Diagnostic ultrasound is attractive for imaging internal hemorrhage due to its portability and real-time imaging capability. However, ultrasound B mode has low sensitivity and is unable to show the active extravasation site. This proposal investigates the application of a novel ultrasonic technique in imaging and quantifying active internal bleeding by detecting localized solid tissue vibrations caused by extravasating blood. [unreadable] Audible bruits and palpable thrills caused by underlying soft-tissue vibrations have often been associated with vascular injury. We have observed in preliminary studies that active bleeding sites both in arteries and organs can be imaged ultrasonically using novel signal processing methods specifically designed to detect and characterize local tissue vibrations surrounding these active bleeding sites. We propose to (1) find quantitative differences between the ultrasonic echo ensembles backscattered from vibrating regions surrounding active bleeding sites and those from normal tissue, (2) correlate the underlying fluid dynamic mechanisms associated with bleeding with the characteristics of the surrounding tissue motion and (3) develop a new ultrasound diagnostic mode for imaging internal hemorrhage by refining our signal processing methods. To achieve these aims, vibrations will first be studied in a controlled ex vivo model of injured blood vessels and organs. Experiments will then be performed in vivo in anesthetized juvenile pigs to study vibrations associated with injured arteries, veins and organs. Based on the results of these experiments, appropriate detection criteria for detecting vibrations associated with internal bleeding will be established. [unreadable] [unreadable]